Osteoarthritis (OA) makes up a large proportion of the disability and economic costs in the U.S. The knee is the most common site of OA and is a common cause of disability and the leading indication of total knee replacement in the elderly. There are presently no curative therapies for OA. Recently, increased attention has focused on the use of complementary and alternative medicine (CAM) therapies, such as acupuncture, especially for patients who have failed to respond to more standard therapy. Little is known of the long-term health services utilization and outcomes of patients with knee OA. This study will evaluate the cost effectiveness and overall outcomes of acupuncture for OA treatment.